1. Field of the Invention
The present invention relates to a lighting device, and more particularly, to a lighting device has a microwave detection function for sensing range and velocity of a moving target.
2. Description of the Prior Art
According to modern intelligent smart homecare and energy-saving requirements, a switch of a lamp or strength of illumination of a lamp in most of lighting devices is designed with a power-saving and energy-saving structure. A common low-power miniature sensor is divided into two types—an infrared sensor and a microwave sensor. The infrared sensor is an electronic device which senses a moving object. The infrared sensor senses movement of the object with variation of infrared ray emitted by a human being. The microwave sensor calculates velocity of the moving object by measuring the Doppler signal of the moving object.
But, restricted to the size of the sensor and the direction of beams, the sensor usually hangs outside of the lamp so that a single chip and a switch-option switch can control switching and brightness of a lamp by choosing a switch. When a person enters the sensing range of the infrared sensor externally connected to the lamp, the infrared sensor is triggered to transmit a signal to activate the controller to illuminate.
However, it is necessary to take an indoor layout and an external controller into consideration when the sensor and the controller having functions of power-saving and energy-saving are used in the lamp system. The lamp system used in a house, a school, and an office building is hard to be maintained by an ordinary person. And, power consumption of the lamp system is larger than that of a single lamp.
In addition, it is harder to add an omnidirectional detection function to the infrared sensor and the 2.4 GHz microwave sensor because beam-width of the infrared sensor and the 2.4 GHz microwave sensor is narrower though smaller in size. Some infrared sensors are designed with secondary optics for increasing a detection angle. Decrease in transmitting signal frequency of the microwave sensor increases the beam-width of the antenna field, but the size of the microwave sensor increases as well. Provided that the design of the antenna is altered without changing the transmitting signal frequency, the detection angle may increase with generating side-lobe of the antenna field and a blind angle in detection. So, it is difficult to integrate the sensor and the lamp system into a single module.